Building a symmetrical PSU B1 buffer

I bought a batch of 100 from spencer and they ranged from about 6.5 t0 11. 2.2 is definitely very suspect.

Andrew, when did you start using 1R0? Isn't that a tad low? I used a 0.1% 100 ohm resistor and that seems to work quite nicely. Perhaps 100 ohms doesn't give quite enough resolution though for really close matching, a 10 ohm resistor would allow me to use the 200mV range on the multimeter rather than the 2V range... I assume this is the reason for going with such a low resistor value? Or is it because you can just use the reading without needing to divide by the resistance?

Tony.

I agree.

You do need at least 10R0 to get full resolution on most meters.

My initial measurements were taken with only the shunt of the meter as a load.
 
Before I go tearing into my supplier.

I've just been looking at the datasheet for the 2SK170.

The parameters are quoted at Vds=10V Vgs=0V and Idss=3mA.

That's not too far from what I am seeing.
 

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Before I go tearing into my supplier.

I've just been looking at the datasheet for the 2SK170.

The parameters are quoted at Vds=10V Vgs=0V and Idss=3mA.

That's not too far from what I am seeing.

That is about minimum transconductance expected. 22 milliSiemens is the low side GR(een) grade's bottom Yfs. Anything marked BL(ue) shall vary between 6-12mA IDSS @ 10V VDS with a midway Yfs of 37mS. Else its a bad or fake sample.
 
Little Buggers are not easy to photograph.

I've tried my best - see what you think.

They definitely look "brushed" to me. That would be my first clue that they have been remarked.
 

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No, that one was for blue pcbs hotrod builders. You are here bcs you are making it on your own with some twists even, here is the general original thread. There you wouldn't be adding anything directly relevant up.
 
I'm having a bid of a headache with the delay section.

How much of a delay should this circuit provide ?

For some reason or other the base of my Relay Driver isn't reaching ON for about 10 minutes. If I omit the BC550 I get virtually no delay. I can work around the problem if I could figure out how long the relay should be de-energised for.

The junction of the timing R & C are rising to 12V as I would expect. The issue seems to be the use of the BC550C as a Zener to de-sensitise the relay driver.

I'm not using the BC517 I'm using 2 x BC550Cs connected as a darlington.
 
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